Vikramjit Singh

Mammalian cells preferentially internalize hydrogel nanodiscs over nanorods and use shape-specific uptake mechanisms

Significance Nanoparticles are widely investigated for intracellular drug delivery and molecular imaging and should be designed to maximize cell uptake. Here the effects of particle geometry to maximize nanoparticle uptake by mammalian cells are evaluated. The findings show that uptake is governed by a combination of cell–particle adhesion, strain energy for membrane wrapping around the particle, and local particle concentration at the cell membrane, all of which are particle-shape–dependent. Under typical culture conditions, disc-shaped hydrophilic nanoparticles were internalized more efficiently than nanorods. Interestingly, larger nanodiscs and rods had higher uptake compared with the smallest particles tested. Mechanisms of uptake were also shape- and cell type-specific. These results provide important insights for rational design of nanocarriers to maximize intracellular delivery efficacy. Size, surface charge, and material compositions are known to influence cell uptake of nanoparticles. However, the effect of particle geometry, i.e., the interplay between nanoscale shape and size, is less understood. Here we show that when shape is decoupled from volume, charge, and material composition, under typical in vitro conditions, mammalian epithelial and immune cells preferentially internalize disc-shaped, negatively charged hydrophilic nanoparticles of high aspect ratios compared with nanorods and lower aspect-ratio nanodiscs. Endothelial cells also prefer nanodiscs, however those of intermediate aspect ratio. Interestingly, unlike nanospheres, larger-sized hydrogel nanodiscs and nanorods are internalized more efficiently than their smallest counterparts. Kinetics, efficiency, and mechanisms of uptake are all shape-dependent and cell type-specific. Although macropinocytosis is used by both epithelial and endothelial cells, epithelial cells uniquely internalize these nanoparticles using the caveolae-mediated pathway. Human umbilical vein endothelial cells, on the other hand, use clathrin-mediated uptake for all shapes and show significantly higher uptake efficiency compared with epithelial cells. Using results from both upright and inverted cultures, we propose that nanoparticle internalization is a complex manifestation of three shape- and size-dependent parameters: particle surface-to-cell membrane contact area, i.e., particle–cell adhesion, strain energy for membrane deformation, and sedimentation or local particle concentration at the cell membrane. These studies provide a fundamental understanding on how nanoparticle uptake in different mammalian cells is influenced by the nanoscale geometry and is critical for designing improved nanocarriers and predicting nanomaterial toxicity.

Innovations in Design Through Transformation: A Fundamental Study of Transformation Principles

The act of creating a new product, system, or process is an innovation; the result of excogitation, study and experimentation. It is an inductive and/or deductive process. The inductive process involves studying systems that exist, for example, in nature, patents and products, and inducing,from the behavior of these systems elemental features for innovating novel products. The deductive process involves deducing such aspects from hypothetical concepts and situations where systems or products could exist. By the application of a combined inductive and deductive approach, this paper reports on a methodology for the creation of innovative products with a broader functional repertoire than traditional designs. This breed of innovative products is coined as transformers, transforming into different configurations or according to different states. Current design theory lacks a systematic methodology for the creation of products that have the ability to transform. This paper identifies analogies in nature, patents, and products along with hypothesizing the existence of such products in different environments and situations. Transformation design principles are extracted by studying key design features and,functional elements that make up a transforming product. These principles are defined and categorized according to their roles in general transformations. The principles and categorizations are then validated and applied to conceptualize transforming products as part of an innovative design process.

Swelling behavior of nanoscale, shape- and size-specific, hydrogel particles fabricated using imprint lithography

Recently a number of hydrogel-based micro- and nanoscale drug carriers have been reported including top down fabricated, highly monodisperse nanoparticles of specific sizes and shapes. One critical question on such approaches is whether in vivo swelling of the nanoparticles could considerably alter their geometry to a point where the potential benefit of controlling size or shape could not be realized. Little has been reported on experimental characterization of the swelling behavior of nanoscale hydrogel structures, and current theoretical understanding is largely based on bulk hydrogel systems. Using atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM) capsules, we have characterized the swelling behavior of nano-imprinted hydrogel particles of different sizes and aspect ratios. Our results indicate a size-dependent swelling which can be attributed to the effect of substrate constraint of as-fabricated particles, when the particles are still attached to the imprinting substrate. Numerical simulations based on a recently developed field theory and a nonlinear finite element method were conducted to illustrate the constraint effect on swelling and drying behavior of substrate-supported hydrogel particles of specific geometries, and compared closely with experimental measurements. Further, we present a theoretical model that predicts the size-dependent swelling behavior for unconstrained sub-micron hydrogel particles due to the effect of surface tension. Both experimental and theoretical results suggest that hydrogel swelling does not significantly alter the shape and size of highly crosslinked nanoscale hydrogel particles used in the present study.

Design for Transformation: Theory, Method and Application

Products which transform to reveal new functionality have been a source of fascination and utility for ages. Such products — transformers — have been previously designed employing ad hoc creativity rather than by pursuing any formal design methodology. By incorporating a design methodology and a concept generation tool for transformers, this research not only unearths further utility for these innovative and revolutionary products, but also aids engineers in the design of these devices with dexterity. The success and advantages of transformers result from added functionality while simultaneously using fewer resources and occupying less space. This paper elucidates the foundation of a methodology for the design of such transforming devices. Our basic research on transforming systems involves a combined inductive and deductive approach, uncovering transformation design principles and a novel method for designing transforming products. In the early stages of design, this method employs a unique process to extract customer needs by examining the requirement hierarchy of product usage scenarios. Such an approach broadens the scope of design and aids in identifying opportunities for transforming products while developing process level insights and solutions catering to these needs. During the concept generation phase of design, the method exploits the transformation design principles as a novel tool to complement and expand contemporary concept generation techniques. A unique bicycle accessory which transforms from a lock to a pump and vice versa is provided as an example of the transformational design process.Copyright

Scalable Imprinting of Shape-Specific Polymeric Nanocarriers Using a Release Layer of Switchable Water Solubility

There is increasing interest in fabricating shape-specific polymeric nano- and microparticles for efficient delivery of drugs and imaging agents. The size and shape of these particles could significantly influence their transport properties and play an important role in in vivo biodistribution, targeting, and cellular uptake. Nanoimprint lithography methods, such as jet-and-flash imprint lithography (J-FIL), provide versatile top-down processes to fabricate shape-specific, biocompatible nanoscale hydrogels that can deliver therapeutic and diagnostic molecules in response to disease-specific cues. However, the key challenges in top-down fabrication of such nanocarriers are scalable imprinting with biological and biocompatible materials, ease of particle-surface modification using both aqueous and organic chemistry as well as simple yet biocompatible harvesting. Here we report that a biopolymer-based sacrificial release layer in combination with improved nanocarrier-material formulation can address these challenges. The sacrificial layer improves scalability and ease of imprint-surface modification due to its switchable solubility through simple ion exchange between monovalent and divalent cations. This process enables large-scale bionanoimprinting and efficient, one-step harvesting of hydrogel nanoparticles in both water- and organic-based imprint solutions.

Effect of Shape, Size, and Aspect Ratio on Nanoparticle Penetration and Distribution inside Solid Tissues Using 3D Spheroid Models

Efficient penetration and uniform distribution of nanoparticles (NPs) inside solid tissues and tumors is paramount to their therapeutic and diagnostic success. While many studies have reported the effect of NP size and charge on intratissue distribution, role of shape, and aspect ratio on NP transport inside solid tissues remain unclear. Here experimental and theoretical studies are reported on how nanoscale geometry of Jet and Flash Imprint Lithography-fabricated, polyethylene-glycol-based anionic nanohydrogels affect their penetration and distribution inside 3D spheroids, a model representing the intervascular region of solid, tumor-like tissues. Unexpectedly, low aspect ratio cylindrical NPs (H/D ≈0.3; disk-like particles, 100 nm height, and 325 nm diameter) show maximal intratissue delivery (>50% increase in total cargo delivered) and more uniform penetration compared to nanorods or smaller NPs of the same shape. This is in contrast to spherical NPs where smaller NP size resulted in deeper, more uniform penetration. Our results provide fundamental new knowledge on NP transport inside solid tissues and further establish shape and aspect ratio as important design parameters in developing more efficient, better penetrating, nanocarriers for drug, or contrast-agent delivery.

Adapted Concept Generation and Computational Techniques for the Application of a Transformer Design Theory

Transformers are a class of products with great potential in a number of markets and applications. These are systems that exhibit a change in state to facilitate new or enhanced product functionality. The historical children’s toys known as “transformers” provide a mental picture of this definition. Working examples are vertical lift aircraft that function as helicopters for take-offs but transform to propeller-driven airplanes for point-to-point travel. This paper builds on research into developing principles and design methodologies for the creation of transforming products. We summarize this research and demonstrate an approach for implementing Transformer Design Principles as part of an ideation and computational design process. An application to an Unmanned Aerial Vehicle (UAV-TACMAV) illustrates the utility of the approach.Copyright

Unique size and shape-dependent uptake behaviors of non-spherical nanoparticles by endothelial cells due to a shearing flow.

&NA; The size and shape of nanoparticle (NP) drug carriers can potentially be manipulated to increase the drug delivery efficacy because of their effects on particle margination and interactions with various cells in vivo. It is found in this work that the presence of a physiologically relevant shearing flow rate results in very different size and shape‐dependent uptake behavior of negatively charged, non‐spherical polyethylene glycol (PEG) hydrogel NPs by endothelial cells (ECs) cultured in a microchannel compared to uptake of either identical NPs in static culture or spherical particles in a shear flow. In particular, larger rod‐ and disk‐shaped PEG NPs show more uptake than smaller ones, opposite to the size effect observed for spherical particles in a flow. Moreover, the trend observed in this dynamic uptake experiment also differs from that reported for uptake of similar PEG NPs by ECs in a static culture, where the smaller disks were found to be uptaken the most. These differences suggest that the increasing rotational and tumbling motions of larger‐size non‐spherical NPs in the flow play a dominant role in NP margination and cell interaction, compared to Brownian motion, gravity, and cell membrane deformation energy. These findings suggest that the coupling between NP geometry and shear flow is an important factor that needs to be accounted for in the design of the size and shape of nanocarriers. Graphical abstract Figure. No caption available.

Innovations in Design Through Transformation: A Fundamental Study of tRaNsFoRmAtIoN Principles

The act of creating a new product, system or process is an innovation: the result of excogitation, study and experimentation. It’s an inductive and/or deductive process. The former is a process of studying systems that exist, for example, in nature, patents and products, and inducing from these system behavior and elemental features for innovating novel products. The latter is a process of deducing such aspects from hypothetical concepts and situations where systems or products could exist. Using a combined inductive and deductive approach, this paper reports on a methodology for the creation of innovative products with a much broader functional repertoire than traditional designs. This breed of innovative products possesses a broader functional repertoire by transforming into different configurations. Current design theory lacks a systematic methodology for the creation of products that have the ability to transform. This paper identifies analogies in nature, patents and products along with hypothesizing the existence of such products in different environments and situations. Transformation Design Principles are extracted by studying key design features and functional elements that make up a transforming product. These principles are listed, defined and categorized according to their roles in generic transformations. The principles and categorizations are then validated and applied to conceptualize a transforming product as an example of an innovative design.Copyright

Scalable Fabrication of Low Elastic Modulus Polymeric Nanocarriers With Controlled Shapes for Diagnostics and Drug Delivery

A new process, decoupled functional imprint lithography (D-FIL), is presented for fabricating low elastic modulus polymeric nanocarriers possessing Youngs modulus of bulk material as low as sub-1 MPa. This method is employed to fabricate sub-50 nm diameter cylinders with >3:1 aspect ratio and other challenging shapes from low elastic modulus polymers such as N-isopropylacrylamide (NIPAM) and poly(ethylene glycol) di-acrylate (PEGDA), possessing Youngs modulus of bulk material 1 GPa, and so these polymers used in nanocarrier fabrication in comparison have very low elastic modulus. Monodispersed, shape- and size-specific nanocarriers composed of NIPAM with material elastic modulus of <1 MPa have been fabricated and show thermal responsive behavior at the lower critical solubility temperature (LCST) of ∼32 °C. In addition, re-entrant shaped nanocarriers composed of PEGDA with elastic modulus <10 MPa are also fabricated. Nanocarriers fabricated from PEGDA are shown with model imaging agent and anticancer drug (Doxorubicin) encapsulated in as small as 50 nm cylindrical nanocarriers.